During his press conference at the NATO summit, President Obama defends his campaign ads attacking Mitt Romney's record at Bain Capital.

The president, speaking to reporters in Chicago at the conclusion of a NATO summit there, said that it's perfectly fair to pore through Romney's record at Bain Capital, the private equity firm he had cofounded, since the former Massachusetts governor had made his private sector experience a cornerstone of his campaign.

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President Barack Obama offered a full-throated defense of his campaign's scrutiny of Mitt Romney's private sector career, flatly stating, "This is not a distraction."

"This is not a distraction. This is what this campaign is going to be about," Obama said.

The president said that he thought that private equity played an important role in the economy. (Republicans have noted that Obama's re-election campaign hasn't always been shy in soliciting contributions from individuals in that industry.) But Obama also argued that the primary role for those firms is to maximize its return for investors.

"If your main argument for how to grow the economy is that I knew how to make a lot of money for investors, then you're missing what this job is about," the president said.

The president's remarks come in the aftermath of a friendly fire incident this weekend, when Newark Mayor Cory Booker, a Democratic mayor who's a surrogate for Obama, said that he found "nauseating" the Obama campaign's attacks on Romney's Bain record.

(Obama avoided publicly chiding Booker, calling him an "outstanding mayor" before pivoting to launch an attack on Romney.)

"The reason this is relevant to my campaign is because my opponent, Gov. Romney -- his main calling card for why he should be president is his business experience. He's not going out there touting his experience in Massachusetts; he's saying I'm a business guy, I know how to fix it," Obama said, coyly hinting at the typically-Democratic state where Romney served a single term as governor.

"When you're president -- as opposed the head of a private equity firm -- your job is not simply to maximize profits. Your job is to figure out how everybody in the country has a fair shot," Obama said.

Earlier in the day, the Romney campaign had sought to claim political momentum based off of Booker's comments (and a subsequent defense of them by Harold Ford, Jr., a former Democratic congressman). The Romney team released a video pronouncing Obama's attacks the "Big Bain Backfire."

Romney himself responded to Obama in a statement: "President Obama confirmed today that he will continue his attacks on the free enterprise system, which Mayor Booker and other leading Democrats have spoken out against. What this election is about is the 23 million Americans who are still struggling to find work and the millions who have lost their homes and have fallen into poverty. President Obama refuses to accept moral responsibility for his failed policies. My campaign is offering a positive agenda to help America get back to work."